// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/formats/mp2t/ts_section_pat.h"

#include <vector>

#include "base/logging.h"
#include "media/base/bit_reader.h"
#include "media/formats/mp2t/mp2t_common.h"

namespace media {
namespace mp2t {

    TsSectionPat::TsSectionPat(const RegisterPmtCb& register_pmt_cb)
        : register_pmt_cb_(register_pmt_cb)
        , version_number_(-1)
    {
    }

    TsSectionPat::~TsSectionPat()
    {
    }

    bool TsSectionPat::ParsePsiSection(BitReader* bit_reader)
    {
        // Read the fixed section length.
        int table_id;
        int section_syntax_indicator;
        int dummy_zero;
        int reserved;
        int section_length;
        int transport_stream_id;
        int version_number;
        int current_next_indicator;
        int section_number;
        int last_section_number;
        RCHECK(bit_reader->ReadBits(8, &table_id));
        RCHECK(bit_reader->ReadBits(1, &section_syntax_indicator));
        RCHECK(bit_reader->ReadBits(1, &dummy_zero));
        RCHECK(bit_reader->ReadBits(2, &reserved));
        RCHECK(bit_reader->ReadBits(12, &section_length));
        RCHECK(section_length >= 5);
        RCHECK(section_length <= 1021);
        RCHECK(bit_reader->ReadBits(16, &transport_stream_id));
        RCHECK(bit_reader->ReadBits(2, &reserved));
        RCHECK(bit_reader->ReadBits(5, &version_number));
        RCHECK(bit_reader->ReadBits(1, &current_next_indicator));
        RCHECK(bit_reader->ReadBits(8, &section_number));
        RCHECK(bit_reader->ReadBits(8, &last_section_number));
        section_length -= 5;

        // Perform a few verifications:
        // - Table ID should be 0 for a PAT.
        // - section_syntax_indicator should be one.
        // - section length should not exceed 1021
        RCHECK(table_id == 0x0);
        RCHECK(section_syntax_indicator);
        RCHECK(!dummy_zero);

        // Both the program table and the CRC have a size multiple of 4.
        // Note for pmt_pid_count: minus 4 to account for the CRC.
        RCHECK((section_length % 4) == 0);
        int pmt_pid_count = (section_length - 4) / 4;

        // Read the variable length section: program table & crc.
        std::vector<int> program_number_array(pmt_pid_count);
        std::vector<int> pmt_pid_array(pmt_pid_count);
        for (int k = 0; k < pmt_pid_count; k++) {
            int reserved;
            RCHECK(bit_reader->ReadBits(16, &program_number_array[k]));
            RCHECK(bit_reader->ReadBits(3, &reserved));
            RCHECK(bit_reader->ReadBits(13, &pmt_pid_array[k]));
        }
        int crc32;
        RCHECK(bit_reader->ReadBits(32, &crc32));

        // Just ignore the PAT if not applicable yet.
        if (!current_next_indicator) {
            DVLOG(1) << "Not supported: received a PAT not applicable yet";
            return true;
        }

        // Ignore the program table if it hasn't changed.
        if (version_number == version_number_)
            return true;

        // Both the MSE and the HLS spec specifies that TS streams should convey
        // exactly one program.
        if (pmt_pid_count > 1) {
            DVLOG(1) << "Multiple programs detected in the Mpeg2 TS stream";
            return false;
        }

        // Can now register the PMT.
#if !defined(NDEBUG)
        int expected_version_number = version_number;
        if (version_number_ >= 0)
            expected_version_number = (version_number_ + 1) % 32;
        DVLOG_IF(1, version_number != expected_version_number)
            << "Unexpected version number: "
            << version_number << " vs " << version_number_;
#endif
        for (int k = 0; k < pmt_pid_count; k++) {
            if (program_number_array[k] != 0) {
                // Program numbers different from 0 correspond to PMT.
                register_pmt_cb_.Run(program_number_array[k], pmt_pid_array[k]);
                // Even if there are multiple programs, only one can be supported now.
                // HLS: "Transport Stream segments MUST contain a single MPEG-2 Program."
                break;
            }
        }
        version_number_ = version_number;

        return true;
    }

    void TsSectionPat::ResetPsiSection()
    {
        version_number_ = -1;
    }

} // namespace mp2t
} // namespace media
